Semiconductor device

ABSTRACT

A semiconductor device includes a plurality of semiconductor chips disposed in a vertical form through a spacer, in which a shield layer having a thickness such that an electromagnetic field radiation generated from a generation source of the semiconductor chip can sufficiently be absorbed is disposed between the semiconductor chips.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a U.S. National Phase of International PatentApplication No. PCT/JP2018/037389 filed on Oct. 5, 2018, which claimspriority benefit of Japanese Patent Application No. JP 2017-244239 filedin the Japan Patent Office on Dec. 20, 2017. Each of theabove-referenced applications is hereby incorporated herein by referencein its entirety.

TECHNICAL FIELD

The present technology relates to a semiconductor device applicable, forexample, to a tuner that receives television broadcasting.

BACKGROUND ART

In the case of a semiconductor device in which a plurality ofsemiconductor chips is mounted in one package, a configuration in whichthe plurality of semiconductor chips is disposed in the state of beingaligned horizontally is adopted. In such a conventional semiconductordevice, there is a problem that an area of the semiconductor device islarge. In addition, in a semiconductor device in which a plurality ofsemiconductor chips is disposed in the state of being stacked in thevertical direction, there is a problem that deterioration of thecharacteristics of the semiconductor chips is generated under aninfluence of electromagnetic field interference between thesemiconductor chips attendant on the close disposition of the upper andlower semiconductor chips.

For example, in the case of a tuner device used for reception oftelevision broadcasting (terrestrial broadcasting, satellitebroadcasting, cable television, etc.), a PLL circuit includes an LCresonance type oscillation circuit. For example, for diversityreception, two tuner sections are used. In the case where twosemiconductor chips stacked vertically constitute respective tunersections, the positions where a coil of an LC resonance type oscillationcircuit on each semiconductor chip are the same. Therefore, a magneticflux generated from the coil of the oscillator on one side intersectsthe coil on the other side, resulting in a problem that the oscillationfrequency of the oscillator on the other side fluctuates.

In addition, in PTL 1 described below, a technology in which two or morelayers of spacers different in area are interposed between semiconductorchips is proposed as a technology for avoiding flexure in asemiconductor stacked package.

CITATION LIST Patent Literature

[PTL 1]

JP 2005-243754A

SUMMARY Technical Problems

The technology described in PTL 1 is mainly intended for prevention offlexure and suppression of void, and is not one for restrainingelectromagnetic coupling between the upper and lower semiconductor chipsmentioned above. PTL 1 has a problem in that in the case where, forexample, a metallic film is small in thickness or the frequency of anoise source is low, a sufficient absorption loss of noise may not beobtainable in the metallic film, and a sufficient noise restrainingeffect may not be obtainable. In addition, the metallic film is notelectrically grounded to earth, and the shield effect is limitative.

Accordingly, it is an object of the present technology to provide asemiconductor device in which semiconductor chips are stacked verticallyand which is not influenced by mutual electromagnetic fieldinterference.

Solution to Problems

In order to solve the aforementioned problems, the present technologyprovides a semiconductor device including a plurality of semiconductorchips disposed in a vertical form through a spacer, in which

a shield layer having a thickness such that an electromagnetic fieldradiation generated from a generation source of the semiconductor chipcan sufficiently be absorbed is disposed between the semiconductorchips.

Advantageous Effect of Invention

According to at least one embodiment, notwithstanding a simplestructure, electromagnetic field interference between upper and lowersemiconductor chips can be reduced, and it is possible to provide asmall-type semiconductor device in which two or more semiconductor chipsare stacked. Note that the effect described here is not necessarilylimitative, and the effect may be any one of the effects described inthe present technology or an effect different from them. In addition,the contents of the present technology are not to be construed aslimited by the effects mentioned as examples in the followingdescription.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a sectional view of a first embodiment of the presenttechnology.

FIG. 2 is a schematic diagram used for explanation of a function of ashield layer.

FIG. 3 is a sectional view of a second embodiment of the presenttechnology.

FIG. 4 is a sectional view of a third embodiment of the presenttechnology.

FIG. 5 is a sectional view of a fourth embodiment of the presenttechnology.

FIG. 6 is a block diagram of an application example of the presenttechnology.

FIG. 7 is a sectional view used for explanation of a conventionalsemiconductor device.

FIG. 8 is a schematic diagram used for explanation of problems in theconventional semiconductor device.

FIG. 9 is a sectional view depicting another example of the conventionalsemiconductor device.

DESCRIPTION OF EMBODIMENTS

The embodiments described below are preferred specific examples of thepresent technology, and technically preferable various limitations areattached thereto. However, the scope of the present technology is notlimited to these embodiments, unless it is specified that the presenttechnology is limited, in the following description.

Note that the description of the present technology will be made in thefollowing order.

<1. Description of problem>

<2. First embodiment of the present technology>

<3. Second embodiment of the present technology>

<4. Third embodiment of the present technology>

<5. Fourth embodiment of the present technology>

<6. Application example>

<7. Modification>

1. Description of Problem

Prior to the description of the present technology, problems in theconventional semiconductor device will be described. A conventionalsemiconductor device 11A depicted in FIG. 7 includes two semiconductorchips 13 a and 13 b of the same configuration disposed on a commonsubstrate 12. The semiconductor chips 13 a and 13 b include variouscircuits (integrated circuits ICs) such as an oscillator, an amplifier,a memory, and a logic. As illustrated in FIG. 7 , a configuration inwhich the semiconductor chips 13 a and 13 b are disposed on a planarbasis has a problem in that a shape (area) of the semiconductor device11A is large.

A conventional semiconductor device 11B in which semiconductor chips 13a and 13 b are disposed in the state of being stacked in the verticaldirection as depicted in FIG. 8 has been known. The semiconductor chip13 a is disposed on a substrate 12, and a spacer 15 is adhered onto thesemiconductor chip 13 a by an adhesive 14 a. The semiconductor chip 13 bis adhered onto the spacer 15 by an adhesive 14 b. The semiconductorchip 13 a and the substrate 12 are connected to each other by wires 16a, and the semiconductor chip 13 b and the substrate 12 are connected toeach other by wires 16 b.

FIG. 9 depicts a schematic diagram of mutual interference due tomagnetic field radiation generated by the circuit. A position of aninductor 21 a of an LC resonance type oscillator included in thesemiconductor chip 13 a and a position of an inductor 21 b of an LCresonance type oscillator included in the semiconductor chip 13 b aresubstantially coincident. An AC current 22 a flows through the inductor21 a, and a magnetic flux 23 is generated by the AC current 22 a. An ACcurrent 22 b may be generated by passing of the magnetic flux 23 throughthe inductor 21 b, which may adversely affect the operation of theoscillator of the semiconductor chip 13 b. The present technology solvessuch a problem.

2. First Embodiment of the Present Technology

FIG. 1 is a sectional view of a semiconductor device 10 according to afirst embodiment. A semiconductor chip 3 a is fixed on a substrate 2 byan adhesive, a silver paste or the like. The semiconductor 3 a includesvarious circuits such as an oscillator, an amplifier, a memory, and alogic, and constitutes, for example, a tuner section of a televisionreception device. This applies also to a semiconductor chip 3 b. Notethat the respective semiconductor chips 3 a and 3 b are not limited tothe configuration in which they include a plurality of ICs or chipparts, and a configuration in which these functions are incorporated ona single chip (SoC (System on a Chip)) may also be adopted.

A spacer 5 is fixed on an upper surface of the semiconductor chip 3 athrough an adhesive 4 a. The spacer 5 includes, for example, a chipobtained by dicing a silicon wafer. A first purpose of providing thespacer 5 is to secure a space for connecting a wire 6 a of the substrate2 to the semiconductor chip 3 a. Therefore, an area of the spacer 5 isset smaller than that of the semiconductor chip 3 a.

A second purpose of disposing the spacer 5 is to secure insulatingproperty such that in the case, for example, where the semiconductorchip 3 a has an analog circuit or a high-speed logic circuit such as anoscillator or amplifier and a comparatively low-resistance substrate isused for the semiconductor chip 3 b, the configuration does notinfluence the operation of the circuit (for example, an LC circuit) ofthe semiconductor chip 3 a. Therefore, the spacer 5 should besufficiently higher in resistance than the substrate of thesemiconductor chip 3 a and have a sufficient thickness. In the firstembodiment, a silicon chip having a specific resistance of 100 Ω·cm anda thickness of 200 μm is used as the spacer 5. In addition, siliconnitride (Si₃N₄) having a specific resistance of greater than 10¹⁴ Ω·cm,silicon carbide (SiC) having a specific resistance of 10⁵ Ω·cm, alumina(Al₂O₃) having a specific resistance of greater than 10¹⁴ Ω·cm, zirconia(ZrO₂) having a specific resistance of greater than 10¹³ Ω·cm, andaluminum nitride (AlN) having a specific resistance of greater than 10¹⁴Ω·cm may also be applicable to the spacer, similarly to theaforementioned silicon.

A shield layer 7 is formed on an upper surface of the spacer 5. Asemiconductor chip 3 b is fixed on an upper surface of the shield layer7 by an adhesive 4 b. The shield layer 7 has a purpose of shielding amagnetic flux generated by an inductor of the semiconductor chip 3 a.The adhesives 4 a and 4 b should include an insulating material,similarly to the spacer 5. For example, the adhesives 4 a and 4 b may bea thin tape having a pressure sensitive adhesive property on both sidesthereof. Specifically, an epoxy-based adhesive was used as the adhesives4 a and 4 b. A silicone-based adhesive, a phenolic adhesive, and acyanoacrylic one may also be applied, similarly to the aforementionedadhesive.

As one example, the shield layer 7 is an aluminum thin film formed bysputtering aluminum on the spacer 5. A similar effect can be obtainedwith a metal with which a high conductivity on the same order of that ofaluminum can be obtained. The shield layer 7 may not necessarily begrounded. Other than a reflection loss of an electromagnetic field dueto a difference in impedance between a peripheral dielectric material(in the present embodiment, silicon of the spacer 5) and the shieldmaterial (in the present embodiment, the shield layer 7 of aluminum),particularly in the case where the frequency of the electromagneticfield is a high frequency band of several gigahertz, an absorption lossin the shield layer 7 can be expected even where the thickness of theshield layer 7 is on the order of several micrometers. Further, ametallic thin film can be produced by sputtering each of copper (Cu),nickel (Ni), gold (Au), and silver (Ag) on the spacer 5. In addition,with the aforementioned metallic material formed by a vacuum depositionmethod, a thin film can be produced and a similar effect can beobtained.

It has been known that an eddy current that generates a magnetic fieldin the opposite direction flows in the shield layer 7 inserted in theform of shielding a magnetic field, as depicted in FIG. 2 , and anabsorption loss is generated. By this absorption of the electromagneticwave, electromagnetic wave energy can be attenuated. With theelectromagnetic wave attenuated, influences on an electronic apparatusand electronic devices is avoided. The absorption loss is represented bythe following formula.20long{e{circumflex over ( )}t/δ} [dB]

Here, δ is a skin depth, is determined by the material of the shieldlayer 7 and the frequency of the electromagnetic field, and isrepresented by the following formula.δ=√(π×frequency×conductivity×permeability) [m]

t is the thickness of the shield layer 7.

In an example in which aluminum is used as the shield layer 7, the skindepth δ when the frequency of the electromagnetic field is 1 GHz is 2.6μm. Further, when (the thickness of the shield layer is t=2.6 μm), thecalculated value of the absorption loss is 8.7 dB.

For example, in the case where the semiconductor chips 3 a and 3 b areboth tuner sections for reception of television broadcasting, signals ofsimilar frequencies of the television frequencies may be received by thetwo semiconductor chips 3 a and 3 b, so that electromagnetic fieldshaving similar frequencies are radiated from the semiconductor chip 3 a.

PLL (Phase Locked Loop) circuits are included in the semiconductor chips3 a and 3 b, in which a coil sensitive to external electromagneticfields and the like are included. In this case, it is preferable todesign the spacer 5, the shield layer 7 and the like in such a mannerthat the total of the reflection loss and the absorption loss will be onthe order of 50 dB. When the thickness of the shield layer 7 designed isset greater than the thickness t (2.6 μm) of the shield used for thecalculated value (8.7 dB) of the aforementioned absorption loss, theelectromagnetic field radiated from the inductor of the semiconductorchip 3 a can be absorbed more. A similar effect to that of aluminum canalso be obtained with copper (Cu), nickel (Ni), and silver (Ag).

The first embodiment of the present technology as aforementioned makesit possible to restrain the magnetic flux generated from the inductorprovided in the semiconductor chip 3 a from passing through the inductorprovided in the semiconductor chip 3 b, and to prevent adverseinfluences from being exerted on the operation of the oscillator of thesemiconductor chip 3 b.

3. Second Embodiment of the Present Technology

FIG. 3 is a sectional view depicting a semiconductor device 20 accordingto a second embodiment of the present technology. In the secondembodiment, the spacer 5 is not provided with a shield layer, and aconductive material is used as the adhesive 4 b. With thisconfiguration, a similar effect to that of the first embodiment isobtained. When the configurations other than the non-formation of theshied layer 7 a and the characteristic properties of the adhesive 4 bare set to be the same as those in the first embodiment aforementioned,an effect to attenuate the electromagnetic field radiated from theinductor of the semiconductor chip can be obtained. Specifically, theconductive adhesive used for electronic and electric uses is anorganic-inorganic mixed material in which conductive particles such asmetallic particulates such as those of aluminum (Al), copper (Cu),silver (Ag), and gold (Au) and metal-plated resin particles areuniformly dispersed in an organic binder such as an epoxy resin.

4. Third Embodiment of the Present Technology

FIG. 4 is a sectional view depicting a semiconductor device 30 accordingto a third embodiment of the present technology. The third embodiment isan embodiment in which the region of the shield layer 7 formed on anupper surface of the spacer 5 is limited. In the case where an aluminumlayer having a wide area is formed as a shield layer, cracking of thealuminum layer called aluminum slide may be generated. In order to avoidthe aluminum slide of the aluminum layer, the shield region of theshield layer 7 may be minimized, whereby an effect to attenuate theelectromagnetic field radiated from the inductor of the semiconductorchip is obtained.

Specifically, the shield layer 7 is formed in the manner of beingrestricted to such a region (area and position) as to be able to coverinterference source circuits (for example, an LC resonance typeoscillator) of the semiconductor chips 3 a and 3 b. Since a radiationnoise diffuses isotropically, the covering range of the shield layer 7should cover a range of an area directly above the interference sourcecircuits to an area reached by addition of the thickness of the spacer.When configurations other than the covering range of the shield layer 7are set to be basically similar to those in the first embodiment, aneffect to attenuate the electromagnetic field radiated from the inductorof the semiconductor chip is thereby obtained.

5. Fourth Embodiment of the Present Technology

FIG. 5 is a sectional view of a semiconductor device 40 according to afourth embodiment of the present technology. In the fourth embodiment,the semiconductor chip 3 a on the lower side is mounted by flip chipmounting, and wire connection between the substrate 2 and thesemiconductor chip 3 a is omitted. The flip chip mounting is one ofmethods for mounting a chip onto a mounting substrate, in which at thetime of electrically connecting between the chip surface and thesubstrate, connection by wires like wire bonding is not adopted, butconnection is conducted by projection-shaped terminals called bumpsarranged in an array, which has a merit that the mounting area can bereduced as compared to the wire bonding. When other configurations thanthe mounting method of the semiconductor chip 3 a are set to bebasically similar to those in the first embodiment, an effect toattenuate the electromagnetic field radiated from the inductor of thesemiconductor chip is thereby obtained.

6. Application Example

The semiconductor devices described as the first to fourth embodimentsabove are applicable, for example, as a tuner section of a receptiondevice for receiving digital terrestrial television broadcasting ordigital satellite broadcasting. As a configuration of a tuner section,there is diversity reception technology as one of effectivecountermeasures against phasing. An electromagnetic wave incommunication undergoes reflection, diffraction, and scattering by beinginfluenced by obstacles and reflectors such as buildings, trees, andground undulations. As a result, a multiplicity of electromagnetic waveshaving passed through various routes interfere with one another, wherebythe intensity of the electromagnetic wave is varied severely. This iscalled phasing. Diversity is a technology in which in regard of the samewireless signal received by a plurality of antennas, the signal of theantenna excellent in electromagnetic wave status is used preferentially,or the received signals are synthesized to remove noise, thereby torealize enhancement of quality and reliability of communication. Sincean electromagnetic wave is reflected on impinging on an object, when acommunicator is used near a large building, for example, there are anelectromagnetic wave reaching the communicator directly and anelectromagnetic wave reaching the communicator after reflection on thebuilding, a difference in arrival time is generated (multi-pass) betweenthe two electromagnetic waves, and the two electromagnetic wavesinterfere with each other, lowering the quality of communication. Forpreventing this, a technology of using two or more antennas to receivethe plurality of electromagnetic waves and selecting the most intenseelectromagnetic wave or synthesizing the electromagnetic waves is calleddiversity. The diversity reception is a technology in which outputs of aplurality of reception systems obtained by disposing a plurality ofantennas at spatially separated positions or by changing the directionor polarization are synthesized or switched, to thereby minimize levelvariations of the electromagnetic wave received. Examples of a syntheticmethod for output in the diversity reception system mainly include amaximum ratio synthetic reception method, a selection synthesisreception method, and an equal gain combining reception method.

In a diversity reception technology, as depicted in FIG. 6 , twoantennas AT1 and AT2 are provided, and outputs of the antennas aresupplied to tuner sections TU1 and TU2. The tuner section TU1 has an RFamplifier 31 for amplifying the output of the antenna AT1, a mixer 32,an oscillator 33, and an A/D converter 34. A reception channel isselected by the mixer 32 and the oscillator 33.

Similarly, the tuner section TU2 has an RF amplifier 41, a mixer 42, anoscillator 43, and an A/D converter 44. The tuner sections TU1 and TU2are configured as semiconductor devices according to the presenttechnology mentioned above. The oscillators 33 and 43 have theconfiguration of an LC oscillator, and have coils. In addition, theoscillators 33 and 43 constitute PLL. By adopting the semiconductordevice of the present embodiment as aforementioned, an effect toattenuate the electromagnetic field radiated from the inductor of thesemiconductor chip is obtained.

Outputs of the tuner sections TU1 and TU2 are supplied to a demodulationand diversity synthetic section 45, processing of OFDM demodulation andthe like are conducted, and a transport stream is formed. Further, inthe demodulation and diversity synthetic section 45, the outputs of thetwo tuner sections are respectively demodulated and thereaftersynthesized. For example, a selector for selecting the outputs of thetwo antennas AT1 and AT2 is provided, and the output of the antenna onone side is selected by an antenna control signal formed in thedemodulation and diversity synthetic section 45. Other than theselection processing, a processing for maximum ratio synthesis of theoutputs of the two antennas AT1 and AT2 can also be performed.

7. Modification

While the embodiments of the present technology have been specificallydescribed above, the present technology is not limited to theaforementioned embodiments, and various modifications are possible basedon the technical thought of the present technology. In addition, theconfigurations, methods, steps, shapes, materials, numerical values andthe like in the aforementioned embodiments may be combined with oneanother, unless departing from the gist of the present technology.

For example, an example in which a silicon chip is used as the spacer 5has been described in the aforementioned embodiments, this is notlimitative, and a similar effect can be obtained also by a configurationin which the spacer 5 includes a material having a high resistance and alow dielectric constant, for example, a glass epoxy substrate (FR-4)substrate. FR-4 is an abbreviation of (Flame Retardant Type 4), andmeans a blank material which is formed by impregnating a cloth of glassfibers with an epoxy resin, followed by a heat-curing treatment toobtain a plate-like body, and which has both flame retardant propertyand low conductivity. A substrate obtained by using a plate of FR4 as abase material and adhering a copper foil thereto is a “glass epoxysubstrate,” which is often used as a material of printed circuit board.In addition, a working example in which aluminum is used as the shieldlayer 7 has been described, this is not limitative, and a similar effectcan be obtained also by use of a material capable of obtaining aconductivity on the order of that of aluminum, such as, for example,gold and copper.

Note that the present technology may take the following configurations.

(1)

A semiconductor device including:

a plurality of semiconductor chips disposed in a vertical form through aspacer, in which

a shield layer having a thickness such that an electromagnetic fieldradiation generated from a generation source of the semiconductor chipthat is capable of sufficiently being absorbed is disposed between thesemiconductor chips.

(2)

The semiconductor device according to (1), in which

the shield layer has a region that corresponds to spreading of theelectromagnetic field radiation due to layout of the generation sourceand the spacer.

(3)

The semiconductor device according to (2), in which

the shield layer is formed in an area and at a position such as to beable to cover the generation source of the semiconductor chip, and acovering range of the shield layer covers a range of an area directlyabove the generation source to an area reached by addition of athickness of the spacer.

(4)

The semiconductor device according to (1), in which

the spacer includes any one of silicon, alumina, zirconia, and aluminumnitride.

(5)

The semiconductor device according to (1) to (4), in which

the shield layer is a metallic thin film.

(6)

The semiconductor device according to (5), in which

the metallic thin film of the shield layer includes any one of aluminum,copper, nickel, and silver.

(7)

The semiconductor device according to any one of (1) to (6), in which

the generation source has an LC resonator including an inductor and acapacitor.

(8)

The semiconductor device according to any one of (1) to (7), in which

the semiconductor chip has an oscillator in which the LC resonator isused.

(9)

The semiconductor device according to any one of (1) to (10), in which

the semiconductor chip constitutes a television broadcasting receivingtuner.

REFERENCE SIGNS LIST

-   -   10, 20, 30, 40 . . . . Semiconductor device    -   2 . . . Substrate,    -   3 a, 3 b . . . . Semiconductor chip    -   4 a, 4 b . . . . Adhesive    -   5 . . . Spacer,    -   6 a, 6 b . . . . Wire    -   7 . . . . Shield layer.

The invention claimed is:
 1. A semiconductor device, comprising: asubstrate; a first semiconductor chip on an upper surface of thesubstrate, wherein the first semiconductor chip comprises a firstgeneration source configured to generate first electromagnetic fieldradiation, and the first generation source is a first oscillator; aspacer on the first semiconductor chip, wherein the spacer includes oneof silicon, alumina, zirconia, or aluminum nitride; a shield layer on anupper surface of the spacer, wherein the shield layer is a metallic thinfilm, and the shield layer is configured to absorb the firstelectromagnetic field radiation; and a second semiconductor chip on anupper surface of the shield layer, wherein the second semiconductor chipcomprises a second generation source configured to generate secondelectromagnetic field radiation, the second generation source is asecond oscillator, each of the first oscillator and the secondoscillator includes configuration of an LC oscillator, and each of thefirst oscillator and the second oscillator constitutes Phase Locked Loop(PLL).
 2. The semiconductor device according to claim 1, wherein theshield layer has a region that corresponds to spread of the generatedfirst electromagnetic field radiation due to layout of the firstgeneration source and the spacer.
 3. The semiconductor device accordingto claim 2, wherein the shield layer covers the first generation sourceof the first semiconductor chip, and the shield layer covers a range ofan area that includes a first area that is directly above the firstgeneration source and a second area reached by addition, of a thicknessof the spacer, to the first area.
 4. The semiconductor device accordingto claim 1, wherein the metallic thin film includes one of aluminum,copper, nickel, or silver.
 5. The semiconductor device according toclaim 1, wherein each of the first generation source and the secondgeneration source has an LC resonator including an inductor and acapacitor.
 6. The semiconductor device according to claim 1, wherein thefirst semiconductor chip constitutes a television broadcasting receivingtuner.
 7. The semiconductor device according to claim 1, wherein theshield layer has a thickness greater than 2.6 micrometres (μm).